Smoke detector

Abstract

A smoke detector ( 1 ) has a spherical chamber ( 2 ) including a plurality of holes ( 15,17 ) for allowing smoke and other particles to enter the chamber. The majority of the internal surface ( 3 ) of the chamber ( 2 ) is covered with a high reflectivity Lambertian surface, that is a material that scatters incident light equally in all directions and at all wavelengths. The remaining portion of the internal surface ( 3 ) is coated with a light absorbing material ( 13 ) such as a matt black coating. A scatter sensor ( 9 ) is directed towards the absorbing coating ( 3 ), and an integrating detector ( 5 ) is configured to detect radiation directly from the entire Lambertian surface. A first LED ( 19 ) emits blue light into the chamber ( 2 ), and a second LED ( 21 ) emits infrared light into the chamber. Processing means ( 23, 25 and 27 ) are provided to analyse the signals from the detectors ( 5,9 ), including means for discriminating between signals from the sensors indicative of different frequencies of received radiation. The processing means can distinguish between different smoke types, such as white/grey smoke and black smoke, and can also distinguish between smoke and other particles.

1. A particle detector including:
 a chamber having a substantially high reflectivity substantially Lambertian surface and a radiation absorbing surface, and for receiving particles, 
 radiation emitting means for emitting radiation into the chamber and directly irradiating the substantially high reflectivity substantially Lambertian surface, and 
 radiation detecting means for detecting the effect of the particles on the radiation within the chamber, 
 wherein the radiation detecting means is primarily for detecting absorption of the radiation by the particles, 
 wherein the radiation detecting means has a wide viewing angle to receive radiation directly from a substantial portion of the high reflectivity Lambertian surface, 
 wherein the radiation detecting means is located at the radiation absorbing surface, and 
 wherein the detector further includes a second radiation detecting means primarily for detecting scattering of radiation by the particles, and wherein the second radiation detecting means is sensitive substantially only to radiation in a path between the second radiation detecting means and the radiation absorbing surface. 
 
     
     
       2. A detector according to  claim 1 , wherein the particles include smoke particles. 
     
     
       3. A detector according to  claim 2 , including a second radiation detecting means primarily for detecting scattering of radiation by the particles, and processing means for analysing data from the two radiation detecting means to determine characteristics of the smoke particles in the chamber. 
     
     
       4. A detector according to  claim 2 , including a second radiation detecting means primarily for detecting scattering of radiation by the particles, and processing means for analysing the data from the two radiation detecting means to determine whether smoke particles or other particles are present in the chamber. 
     
     
       5. A detector according to  claim 1 , wherein the high reflectivity Lambertian surface is a majority of the chamber surface. 
     
     
       6. A particle detector according to  claim 5 , wherein the high reflectivity Lambertian surface covers at least 80% of the chamber surface. 
     
     
       7. A detector according to  claim 1 , including a second radiation emitting means for emitting radiation into the chamber, the second radiation emitting means emitting radiation having a wavelength or wavelengths different from the wavelength or wavelengths of the radiation emitted by the first-mentioned radiation emitting means. 
     
     
       8. A detector according to  claim 7 , wherein the first-mentioned radiation emitting means emits blue light and the second radiation emitting means emits infrared radiation. 
     
     
       9. A detector according to  claim 7 , including means for processing signals from the radiation detecting means to obtain data indicative of the detected radiation emitted by the radiation emitting means. 
     
     
       10. A detector according to  claim 9 , wherein the data is obtained by frequency division multiplexing. 
     
     
       11. detector according to  claim 9 , wherein the data is obtained by time division multiplexing. 
     
     
       12. A detector according to  claim 1 , wherein the radiation absorbing surface is black. 
     
     
       13. A detector according to  claim 1 , wherein the chamber includes holes for allowing the admission of particles, at least one of the holes being in the radiation absorbing surface. 
     
     
       14. A detector according  claim 1 , wherein the radiation emitting means is positioned arbitrarily with respect to the radiation detecting means. 
     
     
       15. A detector according to  claim 1 , wherein the radiation emitting means has a beam spread of between about + or −10° and about + or −15°. 
     
     
       16. A detector according to  claim 1 , wherein the radiation detecting means and the chamber are configured such that the radiation detecting means has a direct view of substantially the entire chamber. 
     
     
       17. A detector according to  claim 1 , wherein the chamber is ellipsoidal. 
     
     
       18. A detector according to  claim 1 , wherein the chamber is spherical. 
     
     
       19. A detector according to  claim 1 , wherein the chamber is an integrating sphere. 
     
     
       20. A particle detector according to  claim 1 , wherein the Lambertian surface reflects greater than 90% of said radiation. 
     
     
       21. A particle detector including:
 a chamber having a substantially high reflectivity substantially Lambertian surface and for receiving particles, 
 radiation emitting means for emitting radiation into the chamber, and 
 radiation detecting means for detecting the effect of the particles on the radiation within the chamber, 
 wherein the radiation detecting means is primarily for detecting absorption of the radiation by the particles, and 
 wherein the radiation detecting means has a wide viewing angle to receive radiation directly from a substantial portion of the high reflectivity Lambertian surface; 
 a second radiation emitting means for emitting radiation into the chamber, the second radiation emitting means emitting radiation having a wavelength or wavelengths different from the wavelength or wavelengths of the radiation emitted by the first-mentioned radiation emitting means; 
 means for processing signals from the radiation detecting means to obtain data indicative of the detected radiation emitted by the radiation emitting means; 
 wherein the two radiation emitting means are driven at different frequencies and the processing means includes lock-in amplifiers operative at the different frequencies and for receiving the output of the detecting means. 
 
     
     
       22. A particle detector including:
 a chamber having a substantially high reflectivity substantially Lambertian surface and for receiving particles, 
 radiation emitting means for emitting radiation into the chamber, and 
 radiation detecting means for detecting the effect of the particles on the radiation within the chamber, 
 wherein the radiation detecting means is primarily for detecting absorption of the radiation by the particles, and 
 wherein the radiation detecting means has a wide viewing angle to receive radiation directly from a substantial portion of the high reflectivity Lambertian surface; 
 a second radiation emitting means for emitting radiation into the chamber, the second radiation emitting means emitting radiation having a wavelength or wavelengths different from the wavelength or wavelengths of the radiation emitted by the first-mentioned radiation emitting means; 
 at least one further radiation emitting means, in addition to the first and second radiation emitting means, the further radiation means emitting radiation having a wavelength or wavelengths different from the wavelength or wavelengths of the first or second radiation emitting means. 
 
     
     
       23. A particle detecting method including the steps of:
 providing a chamber having a substantially high reflectivity substantially Lambertian surface and a radiation absorbing surface, and for receiving particles, 
 emitting radiation into the chamber so as to directly irradiate the substantially high reflectivity substantially Lambertian surface, and 
 detecting the effect of the particles on the radiation within the chamber; 
 wherein the step of detecting radiation includes detecting the absorption of radiation by receiving radiation directly from a substantial portion of the high reflectivity Lambertian surface using a first radiation detector located at the radiation absorbing surface; and 
 wherein the step of detecting radiation further includes the step of detecting the scattering of radiation using a second radiation detector that is sensitive substantially only to radiation in a path between the second radiation detector and the radiation absorbing surface. 
 
     
     
       24. A method according to  claim 23 , wherein the particles are smoke particles. 
     
     
       25. A method according to  claim 23 , wherein the step of emitting radiation includes the steps of emitting radiation at two different wavelengths or wavelength ranges. 
     
     
       26. A method according to  claim 25 , wherein one of said wavelengths or wavelength ranges corresponds to that of blue light and the other of the wavelengths or wavelength ranges corresponds to that of infrared radiation. 
     
     
       27. A method according to  claim 25 , including the step of analysing the detected radiation to obtain data indicative of the radiation received at each of the wavelengths or wavelength ranges. 
     
     
       28. A method according to  claim 27 , including the step of deriving from said data signals indicative of the type of particles within the chamber. 
     
     
       29. A method according to  claim 28 , including the step of deriving signals indicative of whether or not the particles are smoke particles. 
     
     
       30. A method according to  claim 23 , wherein the Lambertian surface reflects greater than 90% of said radiation. 
     
     
       31. A particle detecting method including the steps of:
 providing a chamber having a substantially high reflectivity substantially Lambertian surface and for receiving particles, 
 emitting radiation at two different wavelengths or wavelength ranges into the chamber, and 
 detecting the effect of the particles on the radiation within the chamber; 
 wherein the step of detecting radiation includes detecting the absorption of radiation by receiving radiation directly from a substantial portion of the high reflectivity Lambertian surface; 
 analysing the detected radiation to obtain data indicative of the radiation received at each of the wavelengths or wavelength ranges; and 
 emitting radiation of at least a further wavelength or wavelength range, different to said two wavelengths or wavelength ranges. 
 
     
     
       32. A particle detector including:
 a chamber having substantially high reflectivity substantially Lambertian surface and a radiation absorbing surface, and for receiving particles, 
 radiation emitting means for emitting radiation into the chamber and directly irradiating the substantially high reflectivity substantially Lambertian surface, and 
 radiation detecting means for detecting the effect of the particles on the radiation within the chamber, 
 wherein the radiation detecting means is primarily for detecting absorption of the radiation by the particles, 
 wherein the radiation detecting means has a wide viewing angle to receive radiation directly from a substantial portion of the high reflectivity Lambertian surface, 
 wherein the radiation detecting means and the chamber are configured such that the radiation detecting means has a direct view of substantially the entire chamber, 
 wherein the radiation detecting means is located at the radiation absorbing surface, and 
 wherein the detector further includes a second radiation detecting means primarily for detecting scattering of radiation by the particles, and wherein the second radiation detecting means is sensitive substantially only to radiation in a path between the second radiation detecting means and the radiation absorbing surface. 
 
     
     
       33. A particle detecting method including the steps of:
 providing a chamber having a substantially high reflectivity substantially Lambertian surface and a radiation absorbing surface, and for receiving particles, 
 emitting radiation into the chamber so as to directly irradiate the substantially high reflectivity substantially Lambertian surface, and 
 detecting the effect of the particles on the radiation within the chamber using radiation detecting means, the radiation detecting means and the chamber being configured such that the radiation detecting means has a direct view of a region comprising substantially the entire chamber, 
 wherein the step of detecting radiation includes detecting the absorption of radiation by receiving radiation directly from said region, 
 wherein the radiation detecting means is located at the radiation absorbing surface, and 
 wherein the detector further includes a second radiation detecting means primarily for detecting scattering of radiation by the particles, and wherein the second radiation detecting means is sensitive substantially only to radiation in a path between the second radiation detecting means and the radiation absorbing surface.